1. Field
Embodiments of the disclosure relate generally to the field of surface geometries for aerodynamic improvements to aircraft or surfaces having a flow interface and more particularly to embodiments and fabrication methods for rigid riblets having improved damage resistance.
2. Background
Increasing fuel efficiency in modern aircraft is being accomplished through improvement in aerodynamic performance and reduction of structural weight. Recent advances in the use of microstructures such as riblets on aerodynamic surfaces have shown significant promise in reducing drag to assist in reducing fuel usage. Riblets have various forms but advantageous embodiments may be ridge-like structures that minimize drag on the surface of an aircraft. Riblets may be used in areas of a surface of an aircraft where turbulent regions may be present. Riblets may limit circulation causing a breakup of large scale vortices in these turbulent regions near the surface in the boundary layer to reduce drag.
In certain tested applications, riblets have been pyramidal or inverted V shaped ridges spaced on the aerodynamic surface to extend along the surface in the direction of fluid flow. Riblet structures have typically employed polymeric materials, typically thermoplastics. However in service use such as on an aircraft aerodynamic surface, polymers are relatively soft and thus reducing the durability of the surface. Existing solutions with polymeric tips may readily deform hundreds of percent with fingernail pressure and may be unrecoverable. Such structures may be undesirable in normal service use on an aircraft or other vehicle. Additionally aircraft surfaces are typically required to withstand interactions with various chemicals including Skydrol®, a hydraulic fluid produced by Solutia, Inc. In certain applications elastomers that resist or recover from severe deformation created at the tip may be employed to form the riblets. However, many elastomers and other polymers may not be compatible with Skydrol® or other aircraft fluids or solvents.
The practicality of riblets for commercial aircraft use would therefore be significantly enhanced with a riblet structure providing increased durability and aircraft fluids compatibility.